1. Field of the Invention
This invention relates to a display device, particularly to a plasma display panel device with a large bright region.
2. Description of Prior Art
Normally, the electrodes on the front plate of a plasma display panel (herein referred to a PDP) are fabricated by known semiconductor process. These plasma display panels are classified as either transparent type or reflective type in terms of its luminant mechanism. The characteristic of the so-called transparent type PDP is that the fluorescence material is formed on the front plate. On the other hand, in a reflective type PDP, the fluorescence material is formed on the rear plate. The reflective type PDP is the topic of the recently researches.
The electrodes on the front plate comprise a transparent electrode and an auxiliary electrode. The transparent electrode is normally made of indium tin oxide (ITO). The auxiliary electrode is opaque and normally has a tri-layer structure such as Cr/Cu/Cr or Cr/Al/Cr. However, such a conventional electrode structure leads to certain drawbacks for a PDP, it might cause the poor utilization of light in the bright region.
Referring to FIG. 1a, a plasma display panel comprises a pair of parallel substrates including a first substrate 10a and a second substrate 10b. Plural pairs of transparent electrodes 12 parallel to each other are formed on the first substrate 10a and extending along a first direction. Plural pairs of auxiliary electrodes 14 parallel to each other are then formed on the plural pairs of transparent electrodes 12 and extending along the first direction. Further, a dielectric layer 16 is formed to cover the first substrate 10a, the plural pairs of transparent electrodes 12, and the plural pairs of auxiliary electrodes 14. On the second substrate 10b, a plurality of address electrodes 18 parallel to each other are formed thereon and extending along a second direction that is orthogonal to the first direction. A plurality of spacers 20 parallel to the plurality of address electrodes 18 are then formed on the second substrate 10b for defining the discharge space. Finally, a plurality of fluorescence layers 22 are formed between the plurality of spacers 20 for luminescence when the fluorescence layers 22 are radiated by ultraviolet light generated from gas in the discharge space.
Normally, the gas filled in the discharge space between the first substrate 10a and the second substrate 10b is Neon or Xenon. The gas breaks down when a voltage with an appropriate polarity is applied, and is then ionized to produce plasma. The fluorescence material is excited by the ultraviolet light generated by the plasma to produce a visible light, which is then emitted through the front substrate.
Referring to FIG. 1b, each auxiliary electrode 14 is completely adhered on each transparent electrode 12. The area A is the bright region and the area B is the dark region. Because the accuracy limitation of the photolithgraphy process, the edge of the auxiliary electrode can not align with the edge of the transparent electrode. There is a section 15 having a width of about 10xcx9c20 xcexcm between the edges of the auxiliary electrode 14 and the transparent electrode 12. The section 15 is transparent although the auxiliary electrode is opaque. The light may transmit through the section 15, and the contrast of the panel is decreased.
Referring to FIG. 2, a black matrix 30 is added at the dark region in order to increase the contrast of the panel. However, three small bright regions 23, 24, 25 still appear in the dark region while the fluorescence material radiates visible light. The darkness level of the dark region is too high to gain a proper contrast.
Referring to FIG. 3, the black matrix 32 is further added to cover the gap between each pair of transparent electrodes 12 for improving the contrast of the plasma display panel. There is no bright region in the dark region. However, it can not enlarge the bright region for a given size of pixel. Moreover, the auxiliary electrode consist of Cr/Cu/Cr tends to be lifted-off in subsequent processes because of the poor adhesion between Cr and ITO. In addition, the Cr layer may be etched laterally because of the potential difference between Cr and ITO, and therefore, the adhesion between the auxiliary electrode and the transparent electrode may be decreased during the etching process. Further, bubbles might remain while the dielectric layer 16 is formed. These problems significantly affect the fabrication of a large-size PDP since a required evenness for PDP is difficult to achieve.
Accordingly, to solve the problems of the prior arts, an object of this invention is to provide a plasma display panel device which can enlarge the bright region for a PDP with a given pixel size.
Another object of this invention is to provide a plasma display panel device having an auxiliary electrode which is hardly peeled off by external force during the manufacturing process so as to improve the yield.
According to the present invention, a plasma display panel device has a first substrate and a second substrate with a discharge space therebetween, and a plurality of pairs of transparent electrodes formed on the first substrate, each of the transparent electrodes having a sidewall. A reverse slit where no surface discharge occurs is defined between each adjacent pair of transparent electrodes and a discharge slit for surface discharge therebetween is defined between the transparent electrodes of a single pair. The plasma display panel device includes a plurality of auxiliary electrodes provided near the reverse slits and each of the auxiliary electrodes has a first surface and a second surface. The first surface of each auxiliary electrode is in contact with the sidewall of each transparent electrode and the second surface of the auxiliary electrode is in contact with the first substrate so as to establish a direct adhesion between the auxiliary electrode and the first substrate. According to another aspect of the present invention, a panel of a plasma display includes a substrate, a transparent electrode formed on the substrate and having a sidewall, and an auxiliary electrode having a first surface and a second surface. The first surface is in contact with the sidewall of the transparent electrode and the second surface being in contact with the substrate so as to establish a direct adhesion between the auxiliary electrode and the substrate. The transparent electrode further includes an opening thereon for allowing the second surface of the auxiliary electrode to contact with the substrate through the opening.